1. Field of the Invention
This invention relates to a reusable dental syringe having a combination medication carpule and needle cannula and to a slide lock that is movable to either lock the needle cannula at an outwardly extending position relative to the cylinder, at which an injection may be administered, or to release the needle cannula to be automatically retracted within and surrounded by the cylinder, so as to avoid an accidental needle stick and the possible spread of disease.
2. Prior Art
Syringes of the type having a prefilled carpule of fluid medication and a hypodermic needle cannula are well known in the art for injecting such medication from the carpule to a targeted tissue area of a patient. At the conclusion of the injection, the needle cannula typically remains locked in an axially extended position projecting outwardly from the syringe cylinder. In some cases, the syringe may be used to treat a patient having a communicable disease. Medical workers are especially susceptable to accidental and potentially infectious needle sticks due to the careless handling and disposing of the syringe after use. The resulting mini-accident caused by an accidental needle stick typically requires a blood test for such diseases as AIDS and hepatitis. The corresponding cost and inefficiency of testing medical workers who have received such an accidental needle stick result in considerable waste, which may be particularly damaging to a medical facility which is striving for economy.
The following patent, which has been assigned to the assignee of the present patent application, discloses a reusable dental syringe including a prefilled medication carpule and means for retracting a needle cannula after an injection has been administered: U.S. Pat. No. 4,931,040 issued Jun. 5, 1990.